Leahy was born in Montpelier, Vermont, the son of Alba (née Zambon) and Howard Francis Leahy, a printer. His maternal grandparents were Italian, and his father was of Irish ancestry; some of his ancestors came to Vermont during the 19th century to work at quarries.[2]

Leahy married Marcelle Pomerleau in 1962; she is bilingual with French Canadian heritage from Quebec immigrants in Vermont. They reside in a farmhouse in Middlesex, Vermont that they moved to from Burlington, and have three children. Leahy celebrated his fiftieth anniversary with his wife, saying ‘‘We hate it when we’re apart from one another.’’[3] Leahy is legally blind in one eye.

Leahy was elected to the United States Senate for the first time in November, 1974, in the wake of the Watergate scandal that had resulted in the resignation of President Richard M. Nixon in August of that year. He won a close race against Vermont's lone congressman, Richard Mallary. Leahy succeeded retiring 34-year incumbent George Aiken.[4] At 34 years old, he was the youngest Senator in Vermont history.[5] Leahy was nearly defeated in 1980 by Republican Stewart Ledbetter, winning by only 2,700 votes amid Ronald Reagan's landslide victory.[6] In 1986, he faced what was on paper an even stronger challenger in former governor Richard Snelling, but Leahy turned back this challenge, taking 64 percent of the vote. In 1992, Vermont Secretary of StateJim Douglas held him to 54 percent of the vote. Leahy hasn't faced a substantive Republican challenger since then.

During his tenure as Vice-Chairman of the United States Senate Select Committee on Intelligence in 1987, Leahy showed an unclassified draft report on the Iran-Contra affair to a news reporter. At a press conference, Leahy stated, "Even though it was declassified, I was way too careless about it," and accepted blame. Disclosure of that information was against the Intelligence Committee rules, and Leahy said he hastened his already planned departure from the committee because he was so angry at himself.[7]

The 1998 election was noteworthy in that Leahy had the endorsement of his Republican opponent, Fred Tuttle. Tuttle was the lead actor in the movie Man with a Plan, shot in Vermont, in which a farmer decides to run for the House. Tuttle told voters to vote for Leahy because he didn't want to move to Washington D.C. Leahy was touched by this gesture; he once said that Tuttle was the "distilled essence of Vermonthood".

In 2000, Senator Leahy cosigned a letter sent to Appropriations Committee conference members, requesting a delay in implementing Section 304 in H.R. 4392, the Intelligence Authorization Act for Fiscal Year 2001[8] until it could be fully considered by the Senate Committee on the Judiciary. The amendment would introduce new felony crime laws concerning the unauthorized disclosure of information. Leahy and his colleagues indicated this would be in conflict with existing First Amendment rights and Whistleblower Protection Acts.[9][10]

Former Committee Chairman Robert Byrd (D-WV, far right) shakes hands with Secretary of Defense Robert Gates while Sen. Patrick Leahy (D-VT, center right) and Sen. Tom Harkin (D-IA) look on. The hearing was held to discuss further funding for the War in Iraq.

On June 22, 2004, Leahy and Vice PresidentDick Cheney participated in the US Senate class photo. After the vote, Cheney was only talking to Republicans. When Leahy asked him to come over and talk to the Democrats, Cheney upbraided Leahy for the Senator's recent excoriations of Halliburton's activities in Iraq. At the end of the exchange, Cheney told Leahy, "Go fuck yourself".[11][12] Leahy joked about the incident in 2007 when he escorted Bernie Sanders, Vermont's newly elected senator, to the well of the Senate where he was sworn in by Cheney: "When it comes to the vice president, it's always better to be sworn in than to be sworn at."[13]

In 2005, Project on Government Oversight, a government watchdog group, presented Leahy and Senator John Cornyn with its first ever Bi-Partisan Leadership Award in honor of their cooperation on issues of government oversight and transparency, including their co-sponsorship of the OPEN Government Act of 2005, which prevented burying exemptions to the Freedom of Information Act in legislation.[16]

In May 2011, Leahy introduced the Protect IP Act (PIPA) to the Senate. The bill was drafted to give the US government and copyright holders additional tools to fight copyright piracy and counterfeit goods trafficking by foreign rogue websites. Critics of the bill say that it would be ineffective, impede free expression on the internet, and interfere with its infrastructure. Leahy subsequently indicated that he would favor further research into provisions that raised objections.[20]

Leahy has held progressive political positions that are generally in line with those of the state. He has generally supported abortion rights, rejecting proposals to limit minors or those stationed on military bases from having the procedure performed. He has been supported by the NAACP and is outspoken in his support for affirmative action. Leahy has been one of the most gay rights-friendly members of Congress; he has supported the legalization of gay marriage and reducing discrimination against gays and lesbians. Leahy has called for the domestic partners of federal employees to receive the same benefits as heterosexual couples.[24]

Leahy spoke strongly against a proposed constitutional ban on flag burning and on its implications for freedom of speech and expression. He rejects school prayer initiatives and plans for abstinence-only sex education. Leahy has called for a moratorium on the death penalty and more DNA testing for death row inmates. He supports rehabilitation as the goal of prisons and providing treatment instead of punishment for first time offenders. Leahy has generally supported gun control, including requiring background checks at gun shows and allowing for lawsuits against firearms manufacturers. He voted in favor of prohibiting foreign and UN aid that inhibits gun ownership.[24]

Leahy has stated the importance of increasing the prevalence of public health care during times of economic downturn. He voted to increase Medicare benefits and to allow this organization to negotiate lower-priced, bulk prescriptions from pharmaceutical manufacturers. Leahy has broken with Democratic leadership in supporting allowing states to make bulk drug purchases on their own, an idea he has characterized as an important short term solution until Congress can agree on a similar proposal. Leahy has consistently voted to uphold Social Security and has opposed school vouchers.[24]

On taxation, Leahy has consistently supported progressive rates. He has rejected proposals to remove the Estate Tax and Alternative Minimum Tax, and he has spoken out strongly against cutting taxes for the wealthy. Leahy has strongly supported the rights of employees, and has voted to increase the minimum wage and allow for more union organization. He has voted against a free trade proposal, CAFTA, but supported normalizing trade relations with China.[24]

Leahy was a long-time critic of the Iraq War, and spoke in favor of timetables for troop withdrawal, stating that the country needs well-trained employees in both foreign service and private industry to help repair damage to its civilian structure. He has been critical of the PATRIOT Act, even though he has voted to reauthorize altered versions of it.[24] In June 2013, following the disclosure of PRISM and other covert surveillance activities by the National Security Agency, Leahy introduced a bill that would tighten guidelines related to the acquisition of FISA warrants for domestic surveillance and shorten the current FISA authorization by two years.[25]

Leahy is a fan of the Grateful Dead. He has not only attended concerts, but has a collection of the band's tapes in his Senate Offices. Jerry Garcia visited him at his Senate offices, and Leahy gave a tie designed by Garcia to Senator Orrin Hatch (who responded by giving Leahy a Rush Limbaugh tie). Surviving band members Bob Weir and Mickey Hart have participated in fundraisers for Leahy and his Political Action Committee, the Green Mountain Victory Fund. Leahy appeared in a videotaped tribute to the Dead when they received a lifetime achievement award at the 2002 Jammys. His Senate website notes this response to a question from seventh grade students from Vermont's Thetford Academy who asked Leahy which Dead song was his favorite, he replied: "... my favorite is "Black Muddy River" but we always play "Truckin'" on election night at my headquarters."[citation needed]

A big fan of Batman comics, Leahy wrote the forward to The Dark Knight Archives, Volume 1, a 1992 hardcover anthology of the first four issues of the Batman comic book; and the introduction to Green Arrow: the Archer’s Quest, a 2003 hardcover anthology of six issues of the Green Arrow comic book.

^Patrick Leahy (2013-05-18). "Leahy responds to Gitmo criticism". Battleboro Reformer. Archived from the original on 2013-05-18. Mr. Evers and I agree that the status quo at Guantanamo is unacceptable. I was one of few in the Senate who strongly opposed the decision to open the prison a decade ago, and I continue to believe that the prison at Guantanamo must be closed. Mr. Evers apparently missed it, but my most recent statement about the need to close Guantanamo, two weeks ago, is on my website for all to see at leahy.senate.gov/press/gitmo. As I said in that statement, the Guantanamo prison is not necessary to keep America safe, it contradicts our most basic principles of justice, and it undermines our national security.

^Roger Simon (2007-08-01). "Leahy attacks Bush, Roberts". Politico. Archived from the original on 2007-08-26. Retrieved 2013-05-18. Instead, it contains pictures that Leahy, a published photographer, has taken. The centerpiece -- placed, Leahy says, so he can stare into it every day from his desk -- is a haunting one of a man he met in a refugee camp in El Salvador in 1982.

^McDevitt, Caitlin (2012-07-03). "Leahy making another 'Dark Knight' cameo". Politico. Archived from the original on 2013-03-13. Retrieved 2013-05-18. The Vermont Democrat, who’s a big Batman fan, also made an appearance in the “The Dark Knight” a few years ago. In the scene, the Joker, played by Heath Ledger, holds Leahy at knifepoint.